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Title: Oxalic acid biosynthesis is encoded by an operon in Burkholderia glumae

Author
item Nakata, Paul
item HE, CIXIN - Children'S Nutrition Research Center (CNRC)

Submitted to: FEMS Microbiology Letters
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/27/2009
Publication Date: 2/1/2010
Citation: Nakata, P.A., He, C. 2010. Oxalic acid biosynthesis is encoded by an operon in Burkholderia glumae. FEMS Microbiology Letters. 304:177-182.

Interpretive Summary: Oxalic acid is thought to be an essential acid required by some pathogenic microbes to infect crop plants. Thus, if we knew how this acid was made, we might be to stop its production and reduce the infection of crop plants. In this study, we isolated two genes required for oxalic acid biosynthesis, from the bacterium B. glumae. B. glumae is a bacterium that is responsible for rice yield losses in many parts of the world. Through our study, we were able to find out how these two genes are expressed. It is our hope that what we learn about these genes will lead to the development of new ways to combat oxalate secreting microbes and reduce their negative economic impact on our food supply.

Technical Abstract: Although the biosynthesis of oxalic acid is known to occur in a number of bacteria, the mechanism(s) regulating its production remains largely unknown. To date, there is no report on the identification of an oxalic acid biosynthetic pathway gene from bacteria. In an attempt to identify such a gene(s), a mutant screen was conducted using the simple oxalic acid producing phytopathogenic bacterium, Burkholderia glumae. Four mutants that failed to produce oxalic acid were isolated from a transposon-mutagenized B. glumae library and named Burkholderia oxalate defective (bod) 1. DNA sequence analysis revealed that each mutant contained an insertion event at a different site in the same open reading frame (ORF), which we referred to as the oxalate biosynthetic component (obc) A locus. Complementation of the bod1 mutant with the obcA gene; however, resulted only in a partial restoration of the oxalic acid producing phenotype. Further complementation studies utilizing a larger DNA fragment encompassing the obcA locus coupled with deletion mutagenesis, resulted in the identification of another ORF, that we named the obcB locus, which was essential for the higher levels of oxalic acid production. Transcript analysis indicated that both the obcA and obcB are co-expressed and encoded on a single polycistron message.